1. Field of the Invention
The present invention relates generally to an apparatus and method for encoding and decoding. More particularly, the present invention relates to an apparatus and method for setting a point of time when additional information is applied between transmitting/receiving terminals in a mobile communication system.
2. Description of the Related Art
In general, mobile communication systems have developed from voice service systems into systems that are capable of providing data services. These mobile communication systems can provide broadcast services as well as various data services. In the Third-Generation Partnership Project 2 (3GPP2), developments of various standardization tasks for broadcasting services based on Code Division Multiple Access (CDMA) are ongoing. According to CDMA2000 1× Revision D of the various standards proposed for broadcasting services in 3GPP2, a broadcasting service is called Broadcast and Multicast Service (BCMCS). In addition to the CDMA2000 1× Revision D standard, other standards for providing broadcast services are also being created. The applicable parts of the CDMA2000 1× Revision D standard are expressly incorporated herein by reference.
A broadcast service defined and used in the CDMA2000 1× Revision D standard will now be described. In the following description, the BCMCS service based on the CDMA2000 1× Revision D standard is referred to as the broadcast service.
The broadcast service is configured to transmit broadcast data in a block-interleaved frame unit through a channel on the basis of Time Division Multiplexing (TDM). This broadcast service can use an inner code such as a convolution code or turbo code, and an outer code such as a Reed-Solomon (RS) code serving as a well-known error correction code. When TDM is used to transmit the broadcast data, a receiving terminal selectively receives only minimum frames, thereby improving reception efficiency. To avoid a transmission error of successively generated broadcast data, an RS code is used. This RS code is defined in the present CDMA2000 1× Revision D standard.
Next, a method for transmitting broadcast data on the basis of a broadcast service standard will be described in greater detail.
FIG. 1 illustrates an example of time-division transmission based on the broadcast service standard.
As illustrated in FIG. 1, a base station transmits a broadcast service on the basis of TDM to provide the broadcast service. The TDM transmission methods as illustrated in FIG. 1 are divided on an interlace-by-interlace basis. For each interlace, multiplexes and burst lengths are allocated.
Each interlace indicates a slot of a physical channel transmitted in a time-slot unit in a 1× Evolution Data Only (1×EV-DO) system. In this case, the slot indicates an actual data transmission unit. The multiplex has an index for logically dividing the interlace. The burst length is used to indicate the number of repeat transmissions of a logical broadcast channel constructed by an interlace and multiplex method.
The elements A, B, C, D, and so forth of each interlace, indicate a type of service broadcast, that is, a logical channel, respectively. In FIG. 1, Interlace-0 100 comprises four multiplexing channels of A, B, C and D, Interlace-1 102 comprises four multiplexing channels of E, F, G and H, Interlace-2 104 comprises four multiplexing channels of A, K, L and M, and Interlace-3 106 comprises four multiplexing channels of O, P, Q and R.
In a length of each multiplexing channel included in Interlace-0 100, a value of BurstLength0[i] is set to i={0, 1, 2, 3}. A total burst length indicates a sum of burst lengths within each interlace.
However, various parameters for broadcast service transmission are transferred in a Broadcast Overhead Message (BOM). Specifically, additional information is included and transmitted in the BOM. At this time, the BOM is transferred in a broadcast overhead period. A BOM transmission period is defined by Equation (1) below.BOM Transmission Period=Broadcast Overhead Period×256 Slots  (1)
In Equation (1), the broadcast overhead period is set to 7.
The CDMA2000 1× Revision D standard proposes a point of time when the BOM is transferred. However, a point of time when the BOM is actually transmitted and applied, that is, a change time-point, is not defined in the standard. Because the change time-point is not defined in the standard, there is a problem in that a system operates inefficiently in terms of capacity according to a time-point of applying the BOM.
A problem associated with a conventional method will now be described by way of example, wherein it is assumed that a point of time when a sum of burst lengths is ended, is set as a change time-point.
First, a maximum length of the sum of burst lengths within one interlace is 64×16=1024 slots. Accordingly, a maximum value of a time period of one interlace is 1024×4=4096. However, a period of a basic BOM is 7×256=1792 slots as shown in FIG. 2. FIG. 2 illustrates a conventional BOM transmission time. This makes a change time-point unclear. When a new BOM, that is, BOMB, is first transferred at t=1 as shown in FIG. 3, for example, the BOMB is actually applied in a time To according to a total burst length in a transmission and reception standard. FIG. 3 illustrates a conventional application time-point. During an interval of 1≦t≦To in FIG. 3, additional information transferred through the BOM and additional information used for actual transmission and reception have different intervals. These different intervals result in the following problems.
When a receiver first receives the BOMB in a time of t≧1, there is a problem in that a determination cannot be made as to whether a BOM of a total burst length currently being received is a BOM used for actual transmission and reception because a determination cannot be made as to whether the BOMB matches a previously transmitted BOM.
There is another problem in that a relatively long waiting time is required for a service to be newly started when the total burst length is long.
Therefore, if channel information is changed when a broadcast service is started, an initial detection delay occurs because a user cannot know the change time-point.
Accordingly, a need exists for a system and method for effectively and efficiently defining and setting an application time-point.